The locus of the middle points of those chords of the circle x2+y2=4 which subtend a right angle at the origin is
Let the mid-point of chord is (h,k). Also radius of circle is 2. Therefore
OCOB=cos 45o⇒√h2+k22=1√2⇒h2+k2=2
Hence locus is x2+y2=2